This invention pertains to a vehicle having a steerable front frame, a rear frame spaced rearwardly therefrom, a steerable front wheel assembly on the rear frame, and differential steering linkage operatively connected to the front wheel assembly of the rear frame for producing automatic steering of the rear frame assembly to track substantially in the path of the front frame during a turn.
As is known, unsteered rear load supports on long trailers or other load-handling vehicles will not track well in the path of their pulling tractor during a turn. Instead, there is a natural tendency for the rear end of such vehicle to cut inside the path of the towing portion of the vehicle. This produces a dangerous situation since the rear end of the vehicle, cutting inside the curve, presents a hazard to other vehicles.
In the past, various types of steerable rear load supports for vehicles have been designed, but with less than perfect success being achieved. Previous devices have either been incapable of producing the desired degree of proportionate turning of the rear load support to track properly in the path of the towing portion of the vehicle, or have been unduly expensive and complex both in their initial construction and cost and in the maintenance required for later upkeep.
A primary object of the present invention is to provide a novel vehicle having a steerable rear frame which is so constructed as to overcome the above set out disadvantages of previously designed steerable trailers in a simple and effective manner.
More specifically, an object of the invention is to provide a novel vehicle having a steerable front frame and a wheel supported rear frame, which frames are interconnected by an elongate reach manner. A front wheel assembly on the rear frame is steerable relative to the rear frame and a differential steering linkage interconnects the reach member and steerable wheel assembly in such a manner as to produce proportionate turning of the wheel assembly in the same direction as the reach member turns, but in a preselected ratio less than the angular turning, or swinging, of the reach member. With such turning of the steerable wheel assembly on the rear frame being a proportioned degree less than the swinging of the reach member, the rear frame tracks substantially in the path of the front frame during a turn.
Another object of the present invention is to provide novel differential steering linkage mechanism for producing proportioned steering of the rear frame, in which the linkage interconnection is adjustable to produce tracking of the front and rear frames throughout a variety of lengths of loads carried by the vehicle.
A still further object of the invention is to provide such novel differential steering linkage for the rear frame which includes means for adjusting and maintaining a desired longitudinal alignment between the reach member and longitudinal axis of the rear frame during straight pulling of the rear frame.